1. Field of the Disclosure
The present invention relates to a flow deflector arrangement. More particularly the invention relates to a flow deflector arrangement for use in combination with a pipe arrangement secured through a component. The invention finds particular application in a gas turbine engine, where the component is a turbine case.
2. Description of the Related Art
Within a gas turbine engine it is usual to provide a number of service pipes around the case of a turbine within the core part of the engine. The service pipes pass generally radially through respective apertures formed in the turbine case and are secured to the turbine case by respective service pipe assemblies on the outside of the case. The service pipe assemblies each usually comprise a long-reach threaded hex nut which is tightened to secure the service pipe and the assembly in position. As will be appreciated, the service pipes all need to be sealed against the apertures via which they extend through the turbine casing to prevent the leakage of hot gases from within the turbine.
Given that the gas inside a turbine casing is extremely hot during operation of a gas turbine engine (typically approximately 790 Kelvin in the case of the high pressure turbine of an engine), leakage of the gas through the seals at service pipe positions around the turbine case, for example because of seal failure, is problematic because the high pressure of the gas within the turbine creates an outwardly directed jet of concentrated and very hot gas which can damage other engine components provided outside the turbine casing if it should impinge upon them. For example, in some gas turbine engine designs for the aeronautical industry, components of thrust reversing arrangements are often positioned outside the high pressure turbine, and these components can be damaged by exposure to hot gas leaking through service pipe connections.
In order to address the above-described problems associated with leakage of hot gas through the service pipe connections to the turbine, it has been proposed previously to fit flow deflectors to the hex nuts of each service pipe assembly in order to deflect any leakage flow of gas flowing outwardly from the turbine and generally along the pipe arrangement, such that it will not impinge on any vulnerable components outside the turbine. Such flow-deflectors are typically fitted to the hex nuts after the nuts have been tightened to secure the service pipe assemblies, and their use thus complicates assembly and engine service procedures. Additionally, prior art flow deflectors of this type add considerable mass to the engine and to the sensitive interface between internal and external pipes at the turbine case. The mass of the flow deflectors can increase the contact loading of the seals around the service pipe assemblies which can increase the risk of the seals failing through wear. It is also possible for prior art flow deflectors fitted to the hex nuts to work lose over time which can cause damage to the service pipes or other components in the area.